In Figure 2 diagram, this is the outcome of the report designer when running the form (figure 1).

I marked brown circleon the outcome result. It shld generate S$ instead of US$. In the report designer, I type " iif(df_prcur='US$ ',df_fgst,df_gst) " in the report expression box, hoping to get the S$ if the total amount of any invoices is only printed in US$.

I'm not sure whether I have to add the coding line in the form (figure 1) to show the local currency..